Permanent magnet electric machines are well known in the art. They are usually provided with a stator and a rotor coaxially mounted to the stator so as to rotate thereabout.
Some permanent magnet electric machines are provided with an internal stator and an external rotor generally enclosing the stator. When this is the case, the rotor has a generally cylindrical body and the permanent magnets are positioned on the inner surface of the cylindrical body. To properly mount the permanent magnet to the inner surface of the cylindrical body it is conventional to use an adhesive to prevent relative movements of adjacent permanent magnets.
The use of an adhesive between the permanent magnets and the inner surface of the cylindrical body has many drawbacks. First, an adequate adhesive must be selected since the operating temperature of an electric machine may be quite high. Second, the cost associated with the use of an adhesive is quite high when the price of the adhesive, the manual labour costs, the tooling costs and the parts cleaning costs are added. Indeed, for the adhesive to work properly, the mating surfaces of the permanent magnets and the cylindrical body must be properly prepared and cleaned before the adhesive is applied, which is both time consuming and increases the manufacturing cost of the rotor.
An object of the present invention is therefore to provide an improved permanent magnet rotor assembly.
Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.